Telephone-exchange system



B. G. DUNHAM.

TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED DEC. 27, I918.

Patented Oct. 12, 1920.

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iiiidiii iiiilifiL UNITED STATES PATENT'OFFI-CE.

BERT c. DUNHAM, or HAWTHORNE. NEW JERSEY, ASSIGNOR T0 wEsi'nRN ELECTRIC comrm, INCORPORATED, or NEW YORK, N. Y., A CORPORATION OF NEw YORK.

TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent. Pa, f;ente(l Oct. 12, 1920.

Application filed December 27, 1918, Serial No. 288,571.

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matic systems.

An object of the invention is the provision of a line switch, the brushes of which will continue to seek an idle trunk leading to a selector, should a subscriber replace hlS receiver before said idle trunk is found, and which, upon finding said trunk, w ll be again stepped to their normal positions. In accordance with this object, the return of the line switch to normal is preferably controlled by a similar movement of the selector which is stepped from its normal position by a relay energized upon selzure of a trunk leading to the selector and which continues to operate until the normal position is again reached.

Another object is to provide a novel line switch employing a minimum number of relay whereby the construction is simplified and the cost of production reduced.

A switch of the type shown herein is especially adaptable for use in connection with a selector switch, such as disclosed in a joint application of S. B. Williams, Jr., and B. G. Dunham, filed on December 27, 1918, and bearing Serial No. 268,468, but the same may be employed equally as well with selector switches of other types.

' The inventive idea involved is capable of receiving a variety of expressions, one of which, for the purpose of illustrating the It is believed that the invention will be best understood from a detailed description of the operation. Upon the removal of the receiver at substation A, in initiating a call, line relay 200 of the line switch B is energ zed over a circuit from rounded battery, winding of relay 200, bac contact and innermost lower armature of cutoff relay 201, substation apparatus, upper armature and back marginal stepping magnet 202 is then energ zed over a circuit from grounded battery, winding of said magnet, armature and back contact thereof, front contact and armature of llne relay 200 and lowermost brush 203 to ground at the normal terminal thereof, whereupon the brushes of the switch will be stepped to the second set of terminals, the trunks of which lead to one of the first selector switches. Should the selector switch connected to the first test terminal be busy, brush 203 of the line switch B engaging said terminal will be grounded at the back contact of the line relay of the line switch connected to said selector switch, and a circuit will be found for stepping magnet 202 extending from grounded battery, winding of said magnet, armature and back contact thereof, front contact and armature of relay 200, brush 203, armature and back contact of the line relay of said line switch to ground. Magnet 202 being self-interrupting, will again step the brushes of the line switch over the terminal bank until an idle trunk is found, whereupon a circuit is established from grounded-battery, winding of magnet 202, back contact and armature thereof, winding of relay 201 in series with said magnet, brush 204, conductor 304, winding of low resistance relay 307, brush 308 of the selector switch C, back contact and innermost right armature of test relay 303, and right armature of relay 301 to ground. Magnet 202, being marginal and in series with relay 201, will not operate, but relays 201 and 307 will energize and the former relay will extend the subscribers line to the idle selector switch C. Line relay 200 deenergizes and its back contact grounds the test terminal and makes the trunk test busy to all other line switches.

Line relay 309 of the selector switch will energize immediately upon energization of relay 307, due to the circuit extending from contact of relay 201 to ground. The T grounded battery, right winding of relay 309, armature and front contact of relay 307 to ground, and the circuit for relay 309 will be maintained from grounded battery, right winding of relay 309, back contact and innermost lower armature of cutoff relay 310, lower side of the subscribers line, substation a paratus, upper side of subscrlbers line, bac contact and upper'armature of relay 310, left winding of relay 309, brush 311 and coil 312 to round. First slow-torelease relay 305 is t en energized by a circuit extending from grounded battery, winding of relay 305, front contact and armature of line relay 309 to ground. vA dial tone is furnished by coil 312 and the subscriber may now operate his sending device to select a particular group of trunks terminating in the bank of the selector switch C, in accordance with the-operation as set forth in the copending application previously referred to and to which reference is made for a com lete understanding of the operation of sai selector and other switching means not illustrated or described herein for establishing a connection.

Should the subscriber, after initiating a call, hang up his receiver before an idle trunk leadin to the selector switch has been seized, it w1llbe apparent that the line switch will continue to hunt for the idle trunk and-upon finding the same, cutoff relay 201. will be ener "zed as previously described. Relay 307 eing in series with relay 201 also energizes, and at its front contact, closes a circuit for line relay 309 extending from grounded battery, right winding of line relay 309, armature and front contact of relay 307 to ground, and relay 309, in attractlng its armature, energizes slow-to-release relay 305, thus flgrounding conductor 304, leading from cuto relay 201 at the left armature of relay 305, instead of at the back contact and right armature of relay 301 and thereby shunting relay 307. Release of this relay deenergizes the line relay 309 since the line circuit has been broken by replacin the receiver, and, armature of relay 309 c oses the circuit of stepping magnet 313 extending from ounded battery, winding of said magmet, winding of relay 301, right armature o relay 305, back contact and outermost lower armature of relay 310, back contact and armature of relay 309 to ground, and the brushes are stepped onto the second set of terminals. Group relay 320 is then energized over a circuit .extending from grounded battery, winding of relay 320, brush 308, back contact and inner right armature of test relay303, back contact and right. armature of slow-to-release relay 301 to ground, The right armature of group relay 320'puts ground on the set of test terminals associated therewith and test relay 303 is consequently energized by the and back contact and left armature of relay" 305 to ground, the latter relay having become deenergized upon the release of line relay 309. The brushes are now stepped to the next set of terminals and this action takes place each time the brush 316 engages one of.the terminals which finds ground at the right armature of group relay 320. When engaging the test terminals of different groups of trunks in the selector bank, brush 316 finds ground for test relay 303 at the back contacts and armatures of the respective group relays 314, 315 and 321, and stepping magnet 313 continues to operate until the last set of terminals is reached. When this occurs a-eircuit is closed for test relay 303 extending from groundedbattery, right winding of said relay, brush 316, right alternate contact of relay 305, back contact and lowermost armature of relay 310, and back contact and armature of relay 309 to ground, relays 305 and 309 having released when the calling subscriber replaced his receiver. A circuit is now established for magnet 313 extending through its winding, armature and back contact, front, contact and outer left armature of relay 303 to ground at the left alternate contact of relay 305. Magnet 313 steps the brushes of the switch. from ,the la'sttothe first or normal setof terminals whereupon the parts will a ain be in normal position.

Upon the shunting of'relay 307, relays 309 and 305 will release and the circuit for outoff relay 201 of line switch B will be broken at the left armature of relay 305. Stepping magnet 202 is then energized over a circuit extending from grounded battery, winding of ma et 202, armature and back contact thereo lowermost armature and back contact of relay 201, and brush 205 to ground at the armature'and back contact of line relay 200. Stepping magnet 202 continues to operate until the brushes thereof engage the normal terminals, whereupon the operating circuit of said magnet Wlll be broken and the switch will come to rest.

Should the service of substation A be restrictcd, a conductor 207' is employed to connect the middle. lower armature of. cutoff relay 201 of the line switch with brush 206,

so that if an attem t is made to call the central office from this station, in accordance with the practice in the previously, mentioned application, energlzation of cutoff relay-201 will apply said ground to the cen-' tral ofiice trunks and cause the same to test tery, right winding of relay 303, brush 316,

the last test terminal, outermost left armature and front contact of relay 320, conductor 323, brush 206, middle lower armature and front contact of relay 201 to ground, thus causing the Stepping magnet to again operate and return the swltch to normal. The line switch B, however, remains in its actuated position as long as the receiver is oil the switch hook and the subscriber may again manipulate his dial to select an idle trunk leading to'the private branch exchange operator, as set forth 1n said copending application.

What is claimed is:

1. In a telephone exchange system, a telephone line, a line switch connected to sa1d line, a line relay for said switch a stepp ng magnet, a circuit for operating sa1d stepping magnet, a cutoff relay in serles w1th sa1d stepping magnet and energized when an idle trunk is found to extend said line, and acircuit independent of the windmg of sa1d cutofi relay and including the winding of said stepping magnet for returning sa1d line switch to normal. 1 I

2. In a telephone exchange system, a tele phone line, a line switch connected to said line, a line relay for said switch, electro magnetic means for moving sa1d switch, a circuit for operating said electromagnetic means, other electromagnetic means in series with the first named electromagnetic means and energized when an idle trunk is found to extend said line, and a circuit independent of said other electromagnetic means and including the first named electromagnetic means for returning said. line switch to normal.

3. In a telephone exchange system, a telephone line, a line switch connected thereto, a normal terminal for said switch, test terminals associated with said switch, a test brush engaging said normal terminal, a relay. operated upon the selection of said switch, electromagnetic means energized upon operation of said relay over a circuit through said test brush and terminals for stepping said brush from normal until an idle trunk is found, and other electromagnetic means energized upon the finding of an idle terminal for extending said line, and a circuit independent of said other electromagnetic means and including the first named electromagnetic means for returning said switch to engage said normal terminal.

4. In a telephone exchange system, a tele -v phone line, a roup of trunks, switching means connecte to said line for extending the same, means for operating said switch-- eration of the last named means, otherswitching means for extending said line to a trunk of said group, and means at the first named switching means for preventing the seizure of said trunk.

In a telephone exchange system, a telephone line, a group of trunks, switching means connected to said line for extending the same, means for ope'ratin said switchlng means, a relay for exten ing said telephone line upon the termination of the operation of the last named means, other switchmfg means for extending said l1ne to a trunk 0 said, group, and means controlled by the operation of said relay for preventing seizure of said trunk.

6. In a telephone exchan e system, a subscribers line, two groups 0 trunks, a switch having a normal position and automatically operated to extend said subscribers line upon the initiation of a call, a directively controlled switch to which said line is extended for selecting one of said groups of trunks, means at the first named switch for preventing seizure of an idle trunk in the selected group, and means whereby the other group of trunks may 7. In a telephone exchange system, a telephoneline, a line switch connected thereto and automatically operated to seize an idle trunk upon-initiation of a call, a selector switch to which said idle trunk is connected, means at said selector switch for preventing the return of the line switch to normal after the selector switch has been seized, and means for rendering the last named means ineffective should the subscriber replace his receiver before seizure of said. selector switch, whereby said line switch will be refore seizure of said selector switch, and

means for further operating said selector swltch to again return the same to normal whereby the means for preventing return of said line switch to normal will be rendered ineffective.

9. In a telephone exchange system, a telebe selected with'out returning I thefirst named switch to normal.

normal after telephone line, a

phone line, a line switch connected thereto and automatically" operated to seize an idle trunk upon initiation of a call, a selector switch to which said idle trunk is connected, means at said selector switch for preventing return of the line switch to normal after the selector switch has been seized, means for stepping said selector switch, two circuits for operating said stepping means, means actuated upon seizure of said selector switch for operating said stepping means over one of said circuits to move the selector switch from normal should-a subscriber replace his receiver before seizure of said selector switch, and means for further operating said other circuit to again return the same to normal, whereb the means for preventing return of said l1ne switch to normal will be rendered ineffective.

10. In a, telephone exchange system, a

selector switch having a v definite normal position, a line switch connected to said line and operable to extend the same to said selector switch, said line switch also havinga definite normal pomeans for moving said selector switch sition, from its normal pos1t1on should a subscrlber replace h1s recelver before the selector switch has been seized, and means for 'returning the selector switch to its. normal poselector switch over the sition, whereby said line switch 'is also returned to normal.

"11. In a telephone exchange system, a telephone line, 'a selector switch having a definite normal nected to said line and o erable to extend same tosaid selector switc said line switch also having a definite normal position, electromagnetic means at said selector switch for movin the same from its normal position shoul a subscriber replace his receiver before the selector switch has been seized, and means for returning the selector switch to its normal position whereby the line switch is also returned to normal.

12. In a telephone exchange system, a telephone line, a line switch connected to said line and having a normal position, a line relay for saidswitch, a stepping magnet, a circuit for operating said stepping magnet to step said switch fromits normal position, a cutofi relay in series with said steppingmagnet and energized when an idle trunk is found to extend said line, and a circuit including said stepping magnet for returning said switch to normal.

In witness whereof'I hereunto subscribe my name this 20th day of December, A. D. 1918.

BERT G. DUNI-IAM.

osition','.;a line'switch con- 7 

